On the Ferroelectric to Paraelectric Structural Transition of BaTiO₃ Micro-/Nanoparticles and Their Epoxy...

BaTiO₃ is one of the most widely used ceramic components in capacitor formulation due to its exceptional ferroelectric properties. The structural transition from the ferroelectric tetragonal to the paraelectric cubic phase has been studied in both nano- and micro-BaTiO₃ particles. Several experimental techniques were employed for characterization purposes (X-ray diffraction-XRD, laser Raman spectroscopy-LRS, differential scanning calorimetry-DSC and broadband dielectric spectroscopy-BDS). All gave evidence for the structural transition from the polar tetragonal to the non-polar cubic phase in both nano- and micro-BaTiO₃ particles. Variation of Full Width at Half Maximum (FWHM) with temperature in XRD peaks was employed for the determination of the critical Curie temperature (T_c). In micro-BaTiO₃ particles (T_c) lies close to 120 °C, while in nanoparticles the transition is complicated due to the influence of particles' size. Below (T_c) both phases co-exist in nanoparticles. (T_c) was also determined via the temperature dependence of FWHM and found to be 115 °C. DSC, LRS and BDS provided direct results, indicating the transition in both nano- and micro-BaTiO₃ particles. Finally, the 15 parts per hundred resin per weight (phr) BaTiO₃/epoxy nanocomposite revealed also the transition through the peak formation at approximately 130 °C in the variation of FWHM with temperature. The present work introduces, for the first time, a qualitative tool for the determination and study of the ferroelectric to paraelectric structural transition in both nano- and micro-ferroelectric particles and in their nanocomposites. Moreover, its novelty lies on the effect of crystals' size upon the ferroelectric to the paraelectric phase transition and its influence on physical properties of BaTiO₃.